1. Technical Field
The present invention relates to maintenance devices for liquid-ejecting apparatuses and the liquid-ejecting apparatuses.
2. Related Art
An inkjet recording apparatus is known as an example of a liquid-ejecting apparatus. The inkjet recording apparatus includes a recording head (liquid ejection head). A printing operation using the recording head is performed by ejecting ink droplets from the recording head while moving the recording head relative to a recording sheet. In order to perform high-quality printing by reliably ejecting the ink droplets from the recording head, it is necessary to perform cleaning of the recording head at a suitable timing during the printing operation or in a period in which the printing operation is not performed so that defects, such as clogging of nozzle holes, can be remedied or prevented. For this purpose, the inkjet recording apparatus generally includes a maintenance device for the recording head.
The maintenance device includes a wiper having a wiping member composed of an elastic material formed into a rectangular shape, a cap that functions as a lid for capping a nozzle surface of the recording head in order to prevent ink in the nozzles from drying, and a suction pump for generating a negative pressure for sucking out the ink through nozzle holes formed in the nozzle surface. In an ink suction operation, the nozzle surface is capped to form a sealed space and the suction pump is driven to generate a negative pressure in the sealed space. Accordingly, the ink is sucked out through the nozzle holes in the recording head, so that ink with increased velocity, bubbles, etc., can be discharged. Normally, a wiping operation using the wiper is performed after the suction operation, so that ink and paper dust adhering to the nozzle surface can be removed and the liquid meniscus in the nozzle holes can be adjusted. In addition, in the period in which the printing operation is not performed, the nozzle surface is covered with the cap to prevent the ink in the nozzles from drying. A maintenance device having a lock lever for restraining a carriage at a cleaning position so that capping can be performed while the recording head is at a predetermined position is known (for example, JP-A-2002-1977). In this maintenance device, the wiper and the lock lever are driven by the same power transmission mechanism.
In the maintenance device, the wiper, the cap, and the suction pump must be operated individually. However, when individual rotational drive sources are provided, a plurality of rotational drive sources and individual power transmission mechanisms are necessary. As a result, the structure of the maintenance device becomes complex and the size of the maintenance device is increased. Accordingly, JP-A-2003-154686, for example, discloses a maintenance device including a wiper, a cap, and a suction pump that are operated by a common rotational drive source. In this maintenance device, the number of rotational drive sources can be reduced to one. However, when the maintenance device is installed into an inkjet recording apparatus, the rotational drive source must be provided in addition to at least one rotational drive source for feeding and ejecting recording sheets and the rotational drive source for reciprocating the carriage on which the recording head is mounted.
Accordingly, JP-A-2005-144690 and JP-A-10-202916, for example, disclose inkjet printers in which a paper feed motor for driving a paper feed roller and a conveying roller functions also as a rotational drive source for driving a wiper, a cap, and a suction pump included in a maintenance device (maintenance mechanism). In these printers, the paper feed motor is rotated forward for driving the paper feed roller or the conveying roller, and is rotated in the reverse direction for operating the wiper, the cap, or the suction pump. The suction pump is driven when the paper feed motor is rotated in the reverse direction, and is set to a released state when the paper feed motor is rotated forward. Therefore, a negative pressure is not generated when a paper sheet is being fed or ejected.
A clutch mechanism is additionally provided to prevent the rotation of the paper feed motor from being transmitted to an automatic sheet feeder when the carriage is at a home position (during cleaning). According to JP-A-2005-144690 and JP-A-10-202916, a cueing operation for positioning the recording sheet at a predetermined position is performed, the cueing operation including a backfeed process in which the paper feed motor is rotated in the reverse direction. Therefore, a transmission-delaying unit is provided which causes a delay in transmission of rotation by one turn between an input and an output thereof, so that the maintenance device can be prevented from being activated during the backfeed process.
However, since it is necessary to provide the transmission-delaying unit, the structure of the maintenance device becomes complex. In addition, although the reverse rotation of the paper feed motor is allowed within the amount of rotation delayed by the transmission-delaying unit, if the electric motor is rotated in the reverse direction by an amount larger than the amount of rotation delayed by the transmission-delaying unit, the wiper or the cap moves upward. Therefore, if the carriage moves to the home position after the paper feed motor is rotated in the reverse direction by an amount larger than the amount of rotation delayed by the transmission-delaying unit in order to convey the paper sheet, there is a risk that the recording head comes into contact with the wiper or the cap that is moved upward. Accordingly, even if there are demands for rotating the paper feed motor in the reverse direction by an amount larger than the amount of rotation delayed by the transmission-delaying unit in order to, for example, convey the recording sheet backward (backfeed) for purposes other than cueing in the paper conveying operation, such a demand cannot be satisfied. Thus, when a rotational drive source is used in common for the paper conveying mechanism and the maintenance device, the above-described problems must be solved to increase freedom in the control of, for example, moving the recording sheet backward by rotating the paper feed motor in the reverse direction without causing interference between the paper conveying system and the cleaning system.